According to the United Nations, there are over 100 million land mines currently deployed in more than 60 countries. The mines themselves range from large anti-tank mines to small anti-personnel mines and from all metal construction to primarily plastic or even wood. Triggering mechanisms range from direct pressure, to trip wires to magnetic sensors and fiber optics.
In addition, millions of bomblets were deployed as Cluster Bomb Units (CBUs) during wars and military actions. A significant number of these failed to explode and continue to threaten the populations indigenous to the original combat zones. Being largely constructed of metal, unexploded bomblets are readily detectable with existing hand-held metal detectors. However, current metal detectors have no way of discriminating an intact bomblet, which may be buried at depths up to 12 inches, from a bomblet fragment or other piece of shrapnel or metallic debris that is near the surface.
The US Army currently has a deployed mine detector called the AN/PSS-12. This is an inductive type detector that utilizes the creation of eddy currents in a metallic mine to alter the search coil impedance. This detector has served the Army well, but to be reliably detected, mines must be directly below the search head and must contain some metal. Other methods such as ground penetrating radar, infrared, and X-Ray have been investigated to solve the difficult problem of detecting low-metal and no-metal mines.